1. Field of the Invention
The present invention relates to a metal plate coated with a lubricating resin which is preferable as a patch board for protection in order to efficiently carry out in the small hole drilling process of a printed wiring board, and the drilling processing method of the printed wiring board.
2. Description of the Related Art
When through holes are formed by a drill on a laminated printed wiring board in which a metal foil such as copper or the like is laminated on an insulator, a method of carrying out drilling processing by a drill by arranging a water-soluble lubricating immersion sheet on one side or both sides of the above-described laminated substrate and using the sheet as a patch board is disclosed in U.S. Pat. No. 4,781,495 and U.S. Pat. No. 4,929,370. The lubricating immersion sheet used in the method of forming the through holes is obtained by immersing a mixture of glycols such as diethylene glycol, dipropylene glycol, and the like which is a solid water-soluble lubricant, synthetic waxes such as a fatty acid and the like and nonionic surfactants in a porous material such as paper.
On the other hand, a method of drilling by a drill by using a water-soluble matrix polymer of a polyethylene glycol and a polypropylene glycol or a fatty acid ester derivative thereof alone, or a mixture thereof, and arranging a sheet in which the above-described polymer layer is formed, is disclosed (Japanese Patent Application Laid-Open No.4-92488, No.4-92489, No.4-92490, No.4-92491, No.4-92492, No.4-92493, No.4-92494).
Furthermore, a method of using a polyvinyl pyrrolidone, a gum arabic, a poly(sodium acrylate), sodium alginate, a carboxymethyl cellulose derivative, a polyether ester, a polyethylenepolypropylene glycol tolylene diisocyanate copolymer, a mixture of a specified polyalkylene oxide, a specified dicarboxylic acid compound and a diisocyanate compound, and a resin obtained by reacting a copolymer derived from a specified vinyl compound with a dibasic oxygen acid which contains a polyoxyethylene group as another water-soluble matrix polymer, is disclosed (Japanese Patent Application Laid-Open No.5-169400, No.6-344297, No.8-197496, No.10-6298 and No.10-330777).
However, these methods had defects in that although there is surely an effect of prevention of heat caused by a drill and effects of the reduction of roughness of the inner wall of the drilled part of a printed wiring board and the improvement of drill life-time, the immersion in a porous sheet such as paper or the like is deficient, the adhesion property with an aluminum substrate is inferior, the coating film itself is further apt to be sticky, the stickiness of coating film surface occurs easily under high humidity conditions such as summer, and trouble in treatment as a product is generated. According to advanced studies by the inventors of the present application, the above-mentioned problems were considerably improved by addition of an inorganic powder filler, but the problem of the absorption of moisture or the stickiness by wetting was an essentially inevitable problem by the prior art in which the main component of coating film is composed of a water-soluble resin.
Additionally, there has been a strong requirement to reduce costs of a printed wiring board under the demand of lowering cost in recent electronic information instruments. Accordingly, there is a requirement to shorten the drilling processing time and increase the number of sheets produced per hour, and it has been necessary to increase the rotational speed of a drill bit, make the processing speed of drilling higher, increase the number of a printed wiring boards which are processed at the same time, and extend the life time of a drill, etc. For these demands, it is required to design to make the quality thereof high, as the patch board for a protective board which is used in a severe condition of drilling processing so as to improve the precision of drilling position and the smoothness of the inner surface of the hole.
The object of the present invention is to provide a metal plate coated with a lubricating resin being suitable as a patch board for a protective board, wherein the effect of preventing heat generation at the drill bit in drilling, the lubrication effect and the effect of preventing scattering of chips are high, and simultaneously the discharge property of chips is excellent, the drilling processing can be efficiently carried out in high quality, and simultaneously stickiness is not found, in the drilling processing of a printed wiring board by a drill; and drilling processing method of the printed wiring board being used thereof.
The metal plate coated with a lubricating resin according to the first aspect of the present invention comprises: a lubricating resin coating film obtained by coating and curing by heat a resin composition containing a modified polyamide ({circle around (1)}) and a crosslinking curing agent ({circle around (2)}) of the modified polyamide ({circle around (1)}) on at least one side face of the metal plate.
In the metal plate coated with a lubricating resin, the compounding ratio of the above-described modified polyamide ({circle around (1)}) and the above-described crosslinking curing agent ({circle around (2)}) is preferably {circle around (1)}:{circle around (2)}=(60:40) to (85:15) by a mass ratio converted to solid content. In this case, xe2x80x9ca mass ratio converted to solid contentxe2x80x9d means a ratio of mass of each constitutive unit without solvent.
Furthermore, the above-described resin composition preferably contains an inorganic powder filler ({circle around (3)}).
Furthermore, the above-described resin coating film preferably contains the resin composition which is composed of a water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, and a polycarboxylic acid compound ({circle around (5)}).
Further, the above-described polycarboxylic acid compound ({circle around (5)}) is preferably a polymer compound containing a carboxyl group in a polymer chain, particularly a polyolefin-based resin containing a carboxyl group.
The above-described resin composition preferably contains at least one kind of modified olefin-based resin ({circle around (6)}).
The above-described resin composition is selected from a group comprising, for example, a hydrocarbon-based lubricant composed of a liquid paraffin, a paraffin wax, a micro wax, a low polymerization degree polyethylene, a chlorinated hydrocarbon or a fluorocarbon, a fatty acid-based lubricant composed of a higher fatty acid or an oxy fatty acid, a fatty acid amide-based lubricant composed of a fatty acid amide or an alkylene fatty acid amide, an ester-based lubricant composed of a lower alcohol ester of a fatty acid, a polyhydric alcohol ester of a fatty acid, a polyglycol ester of a fatty acid or a fatty alcohol ester of a fatty acid, an alcohol-based lubricant composed of fatty alcohols, a metal soap-based lubricant composed of an alkaline metal salt of a fatty acid having 12 to 18 carbon atoms, a natural wax-based lubricant composed of a carnauba wax, a candelilla wax, a bees wax, an ibota wax or a montan wax, and a mixture thereof, and contains at least one kind of lubricating compound ({circle around (7)}) having a melting point of a range of 50 to 150xc2x0 C.
The metal plate coated with a lubricating resin according to the second invention of the present application comprises: a lubricating resin coating film obtained by coating the resin composition which is composed of a water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, and a polycarboxylic acid compound ({circle around (5)}), on at least one side face of a metal plate.
In the metal plate coated with a lubricating resin, the above-described resin composition preferably contains an inorganic powder filler ({circle around (3)}).
Further, the above-described resin composition preferably contains at least one kind of modified olefin-based resin ({circle around (6)}).
The above-described resin composition is selected from a group comprising, for example, a hydrocarbon-based lubricant composed of a liquid paraffin, a paraffin wax, a micro wax, a low polymerization degree polyethylene, a chlorinated hydrocarbon or a fluorocarbon, a fatty acid-based lubricant composed of a higher fatty acid or an oxy fatty acid, a fatty acid amide-based lubricant composed of a fatty acid amide or an alkylene fatty acid amide, an ester-based lubricant composed of a lower alcohol ester of a fatty acid, a polyhydric alcohol ester of a fatty acid, a polyglycol ester of a fatty acid or a fatty alcohol ester of a fatty acid, an alcohol-based lubricant composed of fatty alcohols, a metal soap-based lubricant composed of an alkaline metal salt of a fatty acid having 12 to 18 carbon atoms, a natural wax-based lubricant composed of a carnauba wax, a candelilla wax, a bees wax, an ibota wax or a montan wax, and a mixture thereof, and preferably contains at least one kind of lubricating compound ({circle around (7)}) having a melting point of a range of 50 to 150xc2x0 C.
The lubricating resin coating film preferably has water-resistance.
The above-described inorganic powder filler ({circle around (3)}) shows swelling property to water, is a complex oxide derived from laminar mineral of silicate, and preferably has a crystal structure containing at least silicon, magnesium, fluorine, lithium, and sodium.
It is preferable that the above-described water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit is a polyethylene glycol, and the above-described polycarboxylic acid compound ({circle around (5)}) is a polyolefin-based resin containing a carboxyl group.
In the present invention, it is preferable that a mold releasing resin composed of a resin composition containing an epoxy-based resin and a silicone-based resin is coated on a face of the above-described metal plate on which the above-described lubricating resin coating film is not coated.
Furthermore, the above-described metal plate is an aluminum alloy plate, and the above-described lubricating resin coating film having a thickness of 5 to 100 xcexcm is preferably formed on at least one face thereof. In this case, the thickness of the above-described aluminum alloy plate is 20 to 400 xcexcm.
The metal plate coated with a lubricating resin of the present invention is used as, for example, a patch board for protection arranged at the proceeding side of a drill of a plurality of printed wiring boards laminated when the small diameter drilling processing is carried out.
The drilling processing method of a printed wiring board according to the present invention comprises the steps of: arranging the metal plate coated with a lubricating resin according to any one of claims 1 to 19 on a face of one or a plurality of printed wiring boards piled to which a drill proceeds, as a patch board for protection; and carrying out drilling by a drill.
The present invention is described in detail below. The metal plate coated with a lubricating resin which is applied to the first drilling processing for a printed wiring board of the present invention is a metal plate in which at least one side face of its surface is coated with a resin composition composed of a mixture in which a modified water-soluble polyamide ({circle around (1)}) and a crosslinking curing agent ({circle around (2)}) of the modified polyamide ({circle around (1)}) are the essential components.
In the above-described resin composition, a thermoplastic resin composition composed of a mixture in which the above-described inorganic powder filler ({circle around (3)}) and/or the water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, and the polycarboxylic acid compound ({circle around (5)}) are the essential components, and/or the above-described modified olefin-based resin ({circle around (6)}) and/or the above-described lubricating compound ({circle around (7)}) may be contained, according to requirement.
The metal plate coated with a lubricating resin which is applied to the second drilling processing for a printed wiring board of the present invention is a metal plate in which at least one side face of its surface is coated with a thermoplastic resin composition composed of a mixture in which the water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, and the polycarboxylic acid compound ({circle around (5)}) are the essential components.
In the above-described thermoplastic resin composition, the above-described inorganic powder filler ({circle around (3)}) and/or the above-described modified olefin-based resin ({circle around (6)}) and/or the above-described lubricating compound ({circle around (7)}) may be contained, according to requirement.
Furthermore, the preferable constitutional ratio shown by a mass ratio converted to solid content is;
{circle around (1)}:{circle around (2)}=(60:40) to (85:15)
{circle around (4)}:{circle around (5)}=(20:80) to (67:33)
({circle around (1)}+{circle around (2)}+{circle around (4)}+{circle around (5)}):{circle around (3)}=(70:30) to (100:0)
({circle around (1)}+{circle around (2)}+{circle around (3)}+{circle around (4)}+{circle around (5)}):{circle around (6)}=(50:50) to (100:0)
({circle around (1)}+{circle around (2)}+{circle around (3)}+{circle around (4)}+{circle around (5)}+{circle around (6)}):{circle around (7)}=(50:50) to (100:0).
Furthermore, a leveling agent or a defoaming agent may be further compounded in the above-described lubricating resin composition, if necessary, in order to improve coating property to a metal plate.
Furthermore, the lubricating resin coating film formed by coating these resin compositions on a metal plate and curing them by heat is cured by the curing agent ({circle around (2)}), and since the ether bonding of the water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, and the carboxylic group of the polycarboxylic acid compound ({circle around (5)}) form an aggregate caused by hydrogen bonding, it is characterized in that the water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, and the polycarboxylic acid compound ({circle around (5)}) reveal thermoplasticity having a melting point at about 50 to 70xc2x0 C., do not show solubility in water, and have water-resistance.
Furthermore, xe2x80x9chaving water-resistancexe2x80x9d in the present invention means that the dissolution of the coating film does not occur when the lubricating resin coating film is wetted by water. The coating method to a metal plate is not specifically limited, but a production method such as a gravure coat method or a roll coat method is preferable from the viewpoint of productivity, and the metal plate coated with a lubricating resin having a homogeneous coating thickness after heating and quality without stickiness can be obtained by the method.
The above-described modified polyamide ({circle around (1)}) shows solubility in water, and Shore hardness HSD at room temperature is preferably 20 to 40. When the Shore hardness HSD exceeds 40, the hardness of the lubricating resin coating film after heating becomes too high, and the positional precision deteriorates at the time of drilling processing, lubricity at the time of drilling is lowered in particular, therefore a minus effect is imparted from the view point of improvement of a drill life time. On the other hand, when the Shore hardness HSD is less than 20, the hardness and strength of the lubricating resin coating film after heating are insufficient, and the coating film itself happens to be inferior. Accordingly, Shore hardness HSD is preferably 20 to 40.
As the above-described crosslinking curing agent ({circle around (2)}), a melamine-based resin such as methylated methylol melamine, a phenol based resin, and a block isocyanate resin and the like are preferable. It is appropriate that the compounding ratio, {circle around (1)}:{circle around (2)}, of the modified polyamide ({circle around (1)}) and the crosslinking curing agent ({circle around (2)}) is (60:40) to (85:15) by a mass ratio converted to solid content. When the addition ratio of the crosslinking curing agent ({circle around (2)}) is less than 15, the dissolution and swelling of a coating film at the time of exposure to moisture is apt to occur. On the other hand, when the addition ratio exceeds 40, the flexibility of the coating film is lost and the position precision of a hole at the time of drilling processing is lowered. Accordingly, the compounding ratio, {circle around (1)}:{circle around (2)}, is preferably (60:40) to (85:15) by a mass ratio converted to solid content.
The above-described inorganic powder filler ({circle around (3)}) is a complex oxide of laminar silicate whose crystal structure is constituted using at least silicon and magnesium as main elements, and kaolinite or halloysite, pyrophilite, talc, montmorillonite, beidellite, saponite, hectorite, vermiculite, muscovite, phlogopite, tetra silicon mica, margarite, or crinanite or the like which naturally exists, is mentioned. In the present invention, metamorphic mica which is constituted by a crystal structure in which silicon, magnesium, fluorine, and sodium are main elements is mentioned as those showing a remarkable effect in the lubricant resin coating film property and the drilling processing property of the above-described lubricating resin. The metamorphic mica which has this crystal structure shows naturally the swelling property to water, and can bestow excellent characteristics below to the swelling resin and the lubricating resin coating film formed after heating. Firstly, it can be homogeneously dispersed in the lubricating resin by being swelled by water, and the control of the optimum viscosity of the resin composition which can be used for production by a gravure coat method or a roll coat method can be carried out. Secondly, the lubricity of the coating film obtained by the combination of the modified polyamide ({circle around (1)}) which is mainly contained in the above-described lubricating resin coating film lowers the contact area of a drill at the time of drilling processing by forming a fine uneven structure on the surface of the coating film in addition to the lubricity which the metamorphic mica being the above-described inorganic particle has in nature, the lowering of friction is designed to be obtained, and the more lubricity can be imparted. Thirdly, since the above-described metamorphic mica itself has film forming property, and a good coating film can be obtained at the time of coating. In order to further express the above-described three main effects, the mean particle diameter of the above-described metamorphic mica is preferably 1 to 10 xcexcm, furthermore preferably 2 to 8 xcexcm, and most preferably 3 to 5 xcexcm. When the mean particle diameter of the metamorphic mica is less than 1 xcexcm, the uniformity of dispersion in a mixture of the lubricating resin comes to be lowered. On the other hand, when it exceeds 10 xcexcm, the formation of a fine uneven structure on the surface of the coating film becomes difficult, the effect of lubrication is lowered, and precipitation happens to occur during storage of the mixture of the lubricating resin. Accordingly, the mean particle diameter of the metamorphic mica is preferably 1 to 10 xcexcm.
The above-described water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit is an organic compound having an ether bonding in a molecule. Specifically, aqueous lubricants such as polyethylene glycol, a copolymer of polyethylene glycol and polypropylene glycol, polyoxyethylene alkyl ethers, polyoxyethylene sulfosuccinic acid sodium laurylate, fatty acid esters of polyethylene glycol, fatty acid esters of polyoxyethylene sorbitan, fatty acid esters of polyoxyethylene sorbit, polyoxyethlene polyoxypropylene alkyl ether, polyester polyols or polyether polyols composed of ethylene oxide and propylene oxide, are mentioned, and these alone or a combination thereof may be used. Among these, polyethylene glycol is most preferable. The molecular weight is preferably 750 to 400000, more preferably 3400 to 150000, and most preferably 20000 to 40000. When the molecular weight of the water-soluble lubricant which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit is less than 750, stickiness is apt to occur in the lubricating resin coating film after heating. On the other hand, when the molecular weight of the water-soluble lubricant exceeds 400000, the viscosity of the resin composition becomes markedly high, the leveling property of a coating film at the time of coating is lowered, and workability is lowered. Accordingly, the molecular weight of the water-soluble lubricant composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit is preferably 750 to 400000.
The above-described polycarboxylic acid compound ({circle around (5)}) is a high polymer compound containing a carboxyl group in the polymer chain, preferably a polyolefin-based resin containing a carboxyl group, and an ethylene-acrylic acid copolymer, poly acrylic acid and the like can be used. Regarding the water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, and the polycarboxylic acid compound ({circle around (5)}), since the ether bonding of the water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, and the carboxylic group of the polycarboxylic acid compound ({circle around (5)}) form an aggregate caused by hydrogen bonding, the water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, and the polycarboxylic acid compound ({circle around (5)}) show thermoplasticity having a melting point at about 50 to 70xc2x0 C., do not show solubility in water, and have water-resistance. The above-described aggregate is melted by the friction heat generated at the time of drilling processing by a drill, the melted resin carries out lubrication action at the time of drilling processing, therefore it has a characteristic that the roughness of the inner wall of a hole formed by drilling processing is reduced.
It is appropriate that the compounding ratio, ({circle around (4)}:{circle around (5)}), of the water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, and the polycarboxylic acid compound ({circle around (5)}) which is high polymer compound containing a carboxyl group in the molecule is (20:80) to (67:33) by a mass ratio converted to solid content. When the compounding ratio of the water-soluble lubricant ({circle around (4)}) is less than 20, the melting point of the aggregate becomes 90xc2x0 C. or more, it is hardly melted by the friction heat generated at the time of drilling processing by a drill, therefore the lubrication action caused by the melted resin can not be expected. On the other hand, when the above-described polycarboxylic acid compound ({circle around (5)}) is less than 33, the bonding force of the aggregate caused by hydrogen bonding is lowered and water-resistance is degraded, therefore stickiness is apt to occur on the coating film. Accordingly, the compounding ratio, ({circle around (4)}:{circle around (5)}), of the above-described water-soluble lubricant ({circle around (4)}) and the above-described polycarboxylic acid compound ({circle around (5)}) is preferably (20:80) to (67:33) by a mass ratio converted to solid content.
In the above-described resin composition, the above-described modified olefin-based resin ({circle around (6)}) may be added in order to improve the adhesion property of the coating film and the metal plate, and additionally, to improve the position precision of a hole at the time of drilling processing. The modified olefin-based resin ({circle around (6)}) preferably has a Shore hardness HDS of 60 or less, and the adhesion property between the coating film and the metal plate can be improved. As the modified olefin-based resin ({circle around (6)}), a crystalline olefin-based resin, a polyolefin-based resin, an ethylene-ethyl acrylate copolymer, or an ethylene-vinyl acetate copolymer and the like can be used. Furthermore, the modified olefin-based resin ({circle around (6)}) is preferably soluble in water-based solvent, or in a form of water-based emulsion.
The preferable compounding ratio, ({circle around (1)}+{circle around (2)}+{circle around (3)}+{circle around (4)}+{circle around (5)}):{circle around (6)}, of the total of the above-described modified polyamide ({circle around (1)}), the above-described crosslinking curing agent ({circle around (2)}), the above-described inorganic powder filler ({circle around (3)}), the water-soluble lubricant ({circle around (4)}), and the polycarboxylic acid compound ({circle around (5)}), to the above-described modified olefin-based resin ({circle around (6)}) is (50:50) to (100:0) by a mass ratio converted to solid content. When the addition ratio of the above-described modified olefin-based resin ({circle around (6)}) exceeds 50, chips generated at the time of drilling processing are melted by heating, and tend to be adhered in through holes and on the substrate, therefore it causes trouble in discharge and elimination of the chips, or the chips adhere to the drill and it becomes an obstruction at grounding again. Accordingly, it is desirable that the addition ratio of the above-described modified olefin-based resin ({circle around (6)}) is 50 or less.
Furthermore, the above-described lubricating compound ({circle around (7)}) can be added in order to impart more lubricity to the above-described lubricating resin composition. Specific examples of the above-described lubricating compound ({circle around (7)}) include a liquid paraffin, a paraffin wax, a micro wax, a low polymerization degree polyethylene, a chlorinated hydrocarbon or a fluorocarbon, a fatty acid-based lubricant composed of a higher fatty acid or an oxy fatty acid, a fatty acid amide-based lubricant composed of a fatty acid amide or an alkylene fatty acid amide, an ester-based lubricant composed of a lower alcohol ester of a fatty acid, a polyhydric alcohol ester of a fatty acid, a polyglycol ester of a fatty acid or a fatty alcohol ester of a fatty acid, an alcohol-based lubricant composed of fatty alcohols, a metal soap-based lubricant composed of an alkaline metal salt of a fatty acid having 12 to 18 carbon atoms, a natural wax-based lubricant composed of a carnauba wax, a candelilla wax, a bees wax, an ibota wax or a montan wax, and a mixture thereof, and these alone or a mixture thereof may be used. The above-described lubricating compound ({circle around (7)}) expresses its function more by melting due to the friction heat generated at the time of drilling processing by a drill, those having a melting point at a range of 50 to 150xc2x0 C. and more preferably 50 to 90xc2x0 C. are suitable as a lubricant. When the lubricating compound ({circle around (7)}) having a melting point which exceeds 90xc2x0 C. is used, it is hardly melted by the friction heat generated at the time of drilling processing by a drill, therefore an action as a solid lubricant can be expected, but the action caused by the melted lubricant is hardly expected, and the effect is reduced by half. On the other hand, when the melting point is less than 50xc2x0 C., it causes stickiness of the coating film in summer and the like in particular, therefore it is not preferable.
The preferable compounding ratio, ({circle around (1)}+{circle around (2)}+{circle around (3)}+{circle around (4)}+{circle around (5)}+{circle around (6)}):{circle around (7)}, of the total of the above-described modified polyamide ({circle around (1)}), the above-described crosslinking curing agent ({circle around (2)}), the above-described inorganic powder filler ({circle around (3)}), the water-soluble lubricant ({circle around (4)}) which is composed of an ethylene oxide unit or an ethylene oxide unit and a propylene oxide unit, the polycarboxylic acid compound ({circle around (5)}), and the above-described modified olefin-based resin ({circle around (6)}), to the above-described lubricating compound ({circle around (7)}) is (50:50) to (100:0) by a mass ratio converted to solid content. When the addition ratio of the above-described lubricating compound ({circle around (7)}) exceeds 50, chips generated at the time of drilling processing are melted by heating, and tend to be adhered in through holes and on the substrate, therefore it causes trouble in discharge and elimination of the chips, or the chips adhere to the drill and it becomes an obstruction at grounding again. Accordingly, it is desirable that the addition ratio of the above-described lubricating compound ({circle around (7)}) is 50 or less.
Furthermore, a leveling agent or a defoaming agent can be appropriately added for further imparting coating properties to the metal plate in the above-described lubricating resin composition, if necessary.
As a means of coating the lubricating resin composition of the present invention on the metal plate and forming a coating film, a gravure coat method or a roll coat method is preferable from the viewpoint of productivity. The lubricating resin composition coated on the metal plate by such a method is baked in a range of 140 to 250xc2x0 C. and preferably 160 to 200xc2x0 C. for 5 to 120 seconds and preferably 10 to 60 seconds to be dried, and a coating film having a coating thickness of 5 to 100 xcexcm and preferably 10 to 50 xcexcm is formed on the metal plate. When the heating cure temperature is less than 140, the proceeding of the crosslinking reaction o is markedly slow, when the heating cure temperature exceeds 250xc2x0 C., the crystal structure of the metal plate changes and the strength is lowered when the metal plate is an aluminum substrate. Accordingly, the heating cure temperature is preferably 140 to 250xc2x0 C.
The preferable thickness of the lubricating resin coating film is 5 to 100 xcexcm. When the thickness of the coating film is less than 5 xcexcm, lubrication property is not revealed, and when the coating film exceeding 100 xcexcm is formed, coating is difficult and productivity is remarkably lowered because the viscosity of the resin composition must be extremely increased by the above-mentioned two methods.
An aluminum substrate is preferably used as the metal plate. Specifically, there are pure aluminum-based substrate and aluminum alloys such as 3000-based and 5000-based alloy and the like, but the pure aluminum-based substrate is most preferable. The thickness of the aluminum substrate is preferably 20 to 400 xcexcm, more preferably 50 to 250 xcexcm and most preferably 100 to 200 xcexcm. When the thickness of the aluminum substrate is less than 20 xcexcm, the handling property as a patch board becomes worse, and the positional precision of the hole of a drill at the time of drilling processing is lowered. Furthermore, when the thickness of the aluminum substrate exceeds 400 xcexcm, the productivity by the above-mentioned two methods is limited, and it becomes inferior from the view point of economic property.
Furthermore, for the metal plate coated with a lubricating resin, a mold releasing resin composition comprising a resin composition containing a silicone-based resin which is disclosed in Japanese Patent Application Publication No. 4-9 may be coated on the face on which the lubricating resin coating film is not carried out, with a thickness of about 0.5 to 10 xcexcm and further preferably about 1 to 5 xcexcm.
Furthermore, the ratio of the plate thickness T of the metal plate of the aluminum substrate and the like and the thickness tr of the lubricating resin coating film may be appropriately selected in accordance with drilling conditions and the like, but in case of tr/Txe2x89xa60.5, the strain of the metal plate caused by the stress of the lubricating resin coating film becomes minimal, and flatness is improved, therefore an excellent effect of further improving the precision of the drilling processing is obtained. Furthermore, it can be made as an aluminum raw material by melting as it is without peeling the lubricating resin coating film from the metal plate of the aluminum substrate and the like, by setting tr/Txe2x89xa60.5, and the disposal treatment after using it as the patch board for protection is unnecessary, therefore a preferable effect from the viewpoint of the environment is also obtained.
Then, the drilling processing method of the printed wiring board using the metal plate coated with a lubricating resin of the present invention is illustrated. The drilling processing method of the printed wiring board of the present invention is carried out by piling up one or a plurality of the printed wiring boards and arranging the metal plate coated with a lubricating resin of the present invention on the face to which a drill proceeds. The drilling processing method of the printed wiring board is carried out by performing the cutting processing of the metal plate coated with a lubricating resin by a drill and penetrating it.
When a thermoplastic component is contained in the lubricating resin of the metal plate coated with a lubricating resin, friction heat generated from the drilling processing is absorbed by the melting of the lubricating resin, and simultaneously the melted lubricating resin adheres to the drill, and accompanies it in accordance with the proceeding of the drill, therefore the friction at the time of drilling processing is reduced. Thus, cracks can be prevented from occurring in glass fiber, phenol resin, epoxy resin, copper foil, or paper or the like which is the main constitutional component of the printed wiring boards, and severe damage occurs, under the severe drilling processing conditions which have been recently required in particular. Therefore, the abrasion of the drill is reduced, and simultaneously through hole in which the inner wall of hole after the drilling processing is smooth is obtained.
As described in detail above, according to the present invention, the metal plate coated with a lubricating resin film obtained by forming the resin composition of the present invention on the metal plate composed of aluminum and the like as a coating film has an excellent hole positional precision, inner wall roughness, stickiness of the coating film, and water resistance, and can be adequately applied as a patch board at the time of drilling processing of the printed wiring board. Furthermore, the coating film of the lubricating resin composition of the present invention can be formed by a gravure coat method or a roll coat method which is advantageous from the point of productivity, and furthermore, since the coating film formed by heating in a short time is not substantially soluble in water, stickiness does not occur even if it is exposed under high humidity conditions, and even when the coating film once formed on a metal plate is wound up in the form of a roll, then loaded, and unwounded again from the roll, the transcription of the coating film and stable performance can be retained over a long period.